[Coral-List] Darwin was WRONG about reef formation

Thu Oct 22 19:03:56 UTC 2020

Tom:

Thanks for the article. It looks like a great update and I look forward to
reading it.

Dennis

On Wed, Oct 21, 2020 at 5:55 PM <tomascik at novuscom.net> wrote:

> I really enjoyed this exchange. Anyone who may be interested in
> additional information on atolls here are two links you may find
> interesting:
>
>
> https://1drv.ms/b/s!Aq1K6CQCBeATgrUZzsY5CjuHCgLaoQ?e=4icCqy
>
>
> https://www.researchgate.net/publication/303304939_Tomascik_T_A_J_Mah_A_Nontji_M_K_Moosa_1997_Chapter_Sixteen_Atolls_and_Raised_Islands_In_The_Ecology_of_the_Indonesia_Seas_Part_II_pp_751-788_Singapore_Periplus_Editions_HK_Ltd#fullTextFileContent
>
> Cheers,
> Tom
>
> On 2020-10-21 13:08, Douglas Fenner via Coral-List wrote:
> > I think this is a good point, if you define an atoll as a ring of
> > coral at the surface of the water without an island in the center (as
> > we
> > generally do), then there are ways it can form other than a sinking
> > volcano, and an elevated ring left by rainwater dissolving the center
> > of a
> > platform during low sea level is a way in which a ring can form, or on
> > a
> > raised continental block as in the western Caribbean.  On the other
> > hand,
> > Darwin was right about the sequence that happens on subsiding volcanoes
> > on
> > oceanic plates, from fringing to barrier to atoll, but reefs commonly
> > also
> > build on continents, which can also have vertical movements (though
> > usually
> > less total vertical movement).  I just remembered that there are
> > oceanic
> > volcanic islands that do not subside, namely the volcanoes in island
> > arcs
> > behind trenches.  Examples being the windward Antilles in the
> > Caribbean,
> > and Tonga, Vanuatu, and the Marianas in the Pacific.  Those latter
> > three
> > have volcanic islands that have been raised some, with layers of reef
> > limestone raised out of the water that sometimes look like layered
> > cakes
> > from a distance.  The edge of the plate that they are on does not
> > subside,
> > a plate moving down into the trench and going under where the volcanoes
> > are, or other factors, can raise the islands at least enough to lift
> > reefs
> > out of the water.     Cheers,  Doug
> >
> > On Wed, Oct 21, 2020 at 8:22 AM Dennis Hubbard via Coral-List <
> > coral-list at coral.aoml.noaa.gov> wrote:
> >
> >> To some extent, this is probably a matter of semantics. The term
> >> "atoll" is
> >> a geomorphic one - an emergent annular feature built by the
> >> accumulation of
> >> coral and related materials (algae, sediment, etc.). I don't think
> >> there is
> >> any resistance to this. However, from a process standpoint, features
> >> with
> >> this generic shape can result from one of (at least) two very
> >> different
> >> processes. The one we most often acknowledge is a subsiding volcano
> >> that is
> >> cooling and sinking as it moves away from its initial hotspot
> >> location. As
> >> long as reef accretion offsets subsidence, the feature will remain at
> >> or
> >> near to sea level (read Ricky Grigg's paper in an old issue of Coral
> >> Reefs
> >> on his "Darwin Point". .Another alternative is related to wave
> >> refraction
> >> behind an exposed or nearly exposed high on a larger shallow bank. The
> >> resulting wave pattern will create two sedimentary spits on either
> >> side of
> >> (and just downdrift from) the high; this leads to a roughly circular
> >> or
> >> oblate feature resembling its more-common cousins with a volcanic
> >> origin.
> >>
> >> Dennis
> >>
> >> On Mon, Oct 19, 2020 at 9:13 AM Rupert Ormond via Coral-List <
> >> coral-list at coral.aoml.noaa.gov> wrote:
> >>
> >> > Yes I pretty much agree with Doug.
> >> >
> >> > As usual Darwin had the key insight, and unfortunately headlines
> >> > claiming that he was wrong risk inciting conspiracists and
> >> > fundamentalists. Even a hundred years ago we realised from Daly's work
> >> > on Glacial Control Theory that the results of Darwin's geological
> >> > upheavals were likely greatly amended by shorter eustatic processes.
> >> >
> >> > As a result, 50 years ago, I was teaching in classes that ironically
> The
> >> > Australian Great Barrier Reef is not a Barrier Reef, and that the huge
> >> > Atolls of the Maldives are not atolls (despite atoll being a Maldivian
> >> > word in origin) - AT LEAST in the "Darwinian Sense".
> >> >
> >> > Despite this, in the last decade or so I keep seeing people mentioning
> >> > the Great Barrier Reef as the best example of a Barrier Reef, and the
> >> > Maldives as providing the best examples of atolls - perhaps in writing
> >> > by authors whose expertise in newer branches of bioscience left no
> time
> >> > for reading in basic reef biology. Was I wrong all those years??
> >> >
> >> > I guess it all depends what you mean by a barrier reef or an atoll?
> >> >
> >> > cheers,
> >> >
> >> > Rupert
> >> >
> >> > --
> >> > *Prof. Rupert Ormond***
> >> > **
> >> >
> >> > **Co-Director, Marine Conservation International
> >> > Hon. Professor, Centre for Marine Biodiversity & Biotechnology,
> >> > Heriot-Watt University, Edinburgh
> >> >
> >> >
> >> > On 16/10/2020 23:51, Douglas Fenner via Coral-List wrote:
> >> > > or so says a new article:
> >> > >
> >> > > Popular piece:
> >> > >
> >> > > Study: Darwin's theory about coral reef atolls is fatally flawed
> >> > >
> >> > >
> >> >
> >>
> http://news.rice.edu/2020/10/12/study-darwins-theory-about-coral-reef-atolls-is-fatally-flawed-2/
> >> > >
> >> > > Original review:
> >> > >
> >> > > The origin of Modern Atolls: Challenging Darwin's Deeply Ingrained
> >> Theory
> >> > >
> >> > >
> https://www.annualreviews.org/doi/10.1146/annurev-marine-122414-034137
> >> > >
> >> > > My thoughts, based on reading the popular article and the abstract
> for
> >> > the
> >> > > review:
> >> > >
> >> > > Yes, if you define an "atoll" as a ring of coral at the surface, and
> >> you
> >> > > carefully ignore that it is on top of an accumulation of up to a
> mile
> >> of
> >> > > coral reef carbonate, which is in turn on top of a two mile tall
> >> volcano
> >> > > which all the evidence shows has indeed subsided with the ocean
> floor
> >> > plate
> >> > > as it moves across the ocean, then yes, sea level fluctuations with
> the
> >> > > glaciation cycle are widely acknowledged to affect the coral reef
> >> > > structure.  It appears that maybe the new thing in this review is
> that
> >> > the
> >> > > present ring is relatively young and built on top of the raised ring
> >> left
> >> > > from low sea level stands when rainwater was dissolving the
> carbonate
> >> in
> >> > > the center of the ring.  Actually, I don't think even that is new,
> >> though
> >> > > their being a flat topped bank in between time may be new.  This is
> a
> >> > > further embellishment on top of the Darwin theory, NOT a disproof of
> >> his
> >> > > theory, which is heavily documented.  The argument back then was
> >> whether
> >> > > there was a volcano under the carbonate, which drilling proved was
> >> > correct
> >> > > and is no longer in doubt.
> >> > >       Perhaps by reading the entire review it will be clear that the
> >> > review
> >> > > isn't saying that Darwin was wrong about subsidence and a volcano
> being
> >> > > under the carbonate, or that there was a sequence from fringing to
> >> > barrier,
> >> > > to atoll, but even the title of the review implies it is.  But of
> >> course
> >> > > you attract a lot more attention saying that "Darwin was wrong."
> >> > >        What do geologists think?
> >> > > Cheers, Doug
> >> > >
> >> > >
> >> > _______________________________________________
> >> > Coral-List mailing list
> >> > Coral-List at coral.aoml.noaa.gov
> >> > https://coral.aoml.noaa.gov/mailman/listinfo/coral-list
> >> >
> >>
> >>
> >> --
> >> Dennis Hubbard - Emeritus Professor: Dept of Geology-Oberlin College
> >> Oberlin OH 44074
> >> (440) 935-4014
> >>
> >> * "When you get on the wrong train.... every stop is the wrong stop"*
> >>  Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"
> >> _______________________________________________
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> >>
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>

-- 
Dennis Hubbard - Emeritus Professor: Dept of Geology-Oberlin College
Oberlin OH 44074
(440) 935-4014

* "When you get on the wrong train.... every stop is the wrong stop"*
 Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"